The radioassays will be modified as non-radioactive solid phase procedures to measure LH and/or hCG in blood and urine. Enzymes such as horseradish peroxidase, alkaline phosphatase and beta-galactosidase will be used for conjugation to the hormone as markers. Partially purified LH-hCG receptors obtained from bovine corpora lutea and gamma-globulin isolated from specific antisera against LH and hCG will be coupled to porous and non-porous glass or other suitable solid phase for use in the competitive protein binding assays. Non-radioactive procedures will be used in the detection of preovulatory LH surge as well as hCG in early pregnancy and in trophoblastic disease. Recent studies have supported the presence of luteotropic stimulii at the time or prior to implantation. The source, biochemical nature and mode of action of such stimuli will be investigated. hCG, prolactin, estradiol and progesterone will be measured around the time of implantation during the luteal phase by radioassays to determine conception wastage in fertile and infertile women, to determine conception rates in users of IUD and hormonal conception which do not always inhibit ovulation and to develop a model for testing male contraceptives.